You’ve read all of your free items this month. To register, get added benefits and unlimited access to articles, Become a Member. Already a Member? Sign in. Advertising Age Article Abstract 10 Things You Should Know About the Global Ad Market What's The World's Second-Largest Ad Medium? Hint: You're Using It Right Now By Bradley Johnson, Published on December 08, 2013 0 Want more Access, Content & Connections? Upgrade to Membership. We are glad you are enjoying Advertising Age. To get uninterrupted access and additional benefits, become a member today. Register Now Already a member? Log in.